Accommodation function (accommodative power) is very important in the sense of sight. The accommodation function is a function of bringing the sight into focus by changing the refractive power of the eye according to the distance to the object. The crystalline lens, Zinn's zonule, and ciliary body contribute to the change in the refractive power of the eye. The crystalline lens is a convex lens whose refractive power is variable. The Zinn's zunules are tissues that connect the crystalline lens and the ciliary body. The ciliary body is a muscle tissue. To see near objects, the ciliary muscle is contracted while the Zinn's zunules are relaxed. This results in an increase in the thickness of the crystalline lens, thereby the refractive power is increased. On the other hand, to see far objects, the ciliary muscle is relaxed while the tension in the Zinn's zunules increases. This results in reduction of the thickness of the crystalline lens, thereby the refractive power is decreased.
The accommodation function degrades due to the curing of the crystalline lens caused by aging and disease, fatigue of the ciliary muscle, and the like. As the abnormality of the accommodation function, the followings are known: accommodotonia, techno-stress eye disease (visual display terminal syndrome, video display terminal syndrome, or VDT syndrome), Barre-Lieou syndrome, paralysis of accommodation, and the like.
The accommodation function is evaluated based on the amount of aberration and the like in two states achieved by respectively inducing the subject's eye to a far point and a near point using an eye refractive power device or the like.
(Patent Document 1) Re-publication of PCT International Publication No. 2008/129991
(Patent Document 2) Japanese Unexamined Patent Application Publication No. 2000-126132
In such a conventional technology, it has been difficult to structurally evaluate whether the tissues involved in the accommodation function work in a proper way. For example, in the conventional technologies, is has not been comprehensible how the crystalline lens, which provides the accommodative power, operates in practice (i.e., how the shape of the crystalline lens changes). Accordingly, it has been difficult to evaluate the accommodation function in detail.
The object of the present invention is to provide a technology enabling the detailed evaluation of the accommodation function of the subject's eye.
According to one embodiment, an accommodation function evaluation apparatus includes: an accommodative stimulus applying unit configured to apply an accommodative stimulus to an eye; a measurement unit configured to perform optical coherence tomography for a target site in the eye including at least part of the crystalline lens; and an analyzer configured to analyze data obtained by the optical coherence tomography of the eye, to which the accommodative stimulus is being applied, to generate evaluation information related to the accommodation function of the eye.
According to one embodiment of the present invention, the accommodation function of the subject's eye can be evaluated in detail.